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  • 2005-2009  (1)
  • 1995-1999  (3)
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  • 1
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In support of the spiral wave theory of reentry, simulation studies and animal models have been utilized to show various patterns of spiral wave tip motion such as meandering and drifting. However, the demonstration of these or any other patterns in cardiac tissues have been limited. Whether such patterns of spiral tip motion are commonly observed in fibrillating cardiac tissues is unknown, and whether such patterns form the basis of ventricular tachycardia or fibrillation remain debatable. Using a computerized dynamic activation display, 108 episodes of atrial and ventricular tachycardia and fibrillation in isolated and intact canine cardiac tissues, as well as in vitro swine and myopathic human cardiac tissues, were analyzed for patterns of nonstationary, spiral wave tip motion. Among them, 46 episodes were from normal animal myocardium without pharmacological perturbations, 50 samples were from normal animal myocardium, either treated with drugs or had chemical ablation of the subendocardium, and 12 samples were from diseased human hearts. Among the total episodes, 11 of them had obvious nonstationary spiral tip motion with a life span of 〉2 cycles and with consecutive reentrant paths distinct from each other. Four patterns were observed: (1) meandering with an inward petal flower in 2; (2) meandering with outward petals in 5; (3) irregularly concentric in 3 (core moving about a common center); and (4) drift in 1 (linear core movement). The life span of a single nonstationary spiral wave lasted no more than 7 complete cycles with a mean of 4.6±4.3, and a median of 4.5 cycles in our samples. Conclusion: (1) Patently evident nonstationary spiral waves with long life spans were uncommon in our sample of mostly normal cardiac tissues, thus making a single meandering spiral wave an unlikely major mechanism of fibrillation in normal ventricular myocardium. (2) A tendency toward four patterns of nonstationary spiral tip motion was observed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Various methodological approaches are being used to characterize Symbiodinium spp isolated from Marginopora vertebralis and Amphisorus hemprichii and Amphisorus sp. from the Indo-pacific. While most of the cells in culture are non-motile vegetative cells, dinospores occur in batch cultures. We find consistant variance among the isolates in the duration and time of appearance of motile forms. Nitrate (0.146 mM) supports higher populations of the isolates than NH4 (0.146 mM). Higher concentrations of NH4 inhibit growth. Although Fensome et al. (1993) characterized the Order Suessiales (and Family Symbiodiniaceae) as gymnnodiniphycideans in which the amphiesmal vesicals are arranged in 7–10 longitudinal series we were unable to detect any plates on the surfaces of our isolates in the SEM. We were unsuccessful in revealing plates on non-motile forms by freeze fracture but they were present after treatment with various chemical agents (e.g. H2O2, HOCl−) and enzymes (cellulase, chitinase). They are not polygonal or arranged in the patterns anticipated for the Symbiodiniaceae. Polyclonal antibody studies of the Symbiodinium-like isolates are in agreement with molecular systematic studies in the sense that there is a common relation. The foram endosymbiotic dinoflagellates share some common surface antigens with each other and with the few invertebrate isolates we have tested. Studies of the foraminiferal symbionts' plastids revealed considerable morphological diversity. We isolated a diversity of endosymbionts from the mantle of Tridacna maxima from the Red Sea and the Marshall Islands. These included Symbiodinium, Amphidinium, Tetraselmis, and an unidentified chlorophyte.
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  • 3
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The RP14 autosomal recessive Retinitis pigmentosa (arRP) locus has been mapped to a 2cM region of chromosome 6p21.3 (refs 1–3). TULP1 (the gene encoding tubby-like protein 1) is a candidate target for the disease mutation because it maps to the RP14 minimum genetic region and because a ...
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To characterize the signalling molecules produced from the uncleaved Hh precursor U, we determined the site of autoproteolysis and the structures of the cleaved products using a purified Hh protein from a bacterial source. This purified protein, His6C, contains primarily carboxy-terminal sequences ...
    Type of Medium: Electronic Resource
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